Vol 22, No 7

## Multicolor Optical Monitoring of the γ -Ray Emitting Narrow-line Seyfert 1 Galaxy PMN J0948+0022 from 2020 to 2021

#### Yu-Xin Xin, Ding-Rong Xiong, Jin-Ming Bai, Hong-Tao Liu, Kai-Xing Lu and Ji-Rong Mao

Abstract

In order to study the physical properties of the γ-ray emitting narrow-line Seyfert 1 (NLS1) galaxy population, photometric and spectral observations of the γ-ray emitting NLS1 PMN J0948+0022 were made with the Lijiang 2.4 m optical telescope of Yunnan Observatories, Chinese Academy of Sciences. Photometric data in the B and R bands were collected for 50 nights from 2020 January to 2021 December. During the observation epoch, the variability amplitudes are 73.67% in the B band and 79.96% in the R band. Intra-day variability is found in two observation nights, and the duty cycle value is 29% with variability amplitude > 12.9% in the R band, which support the presence of the relativistic jets in the target. The redder-when-brighter (RWB) chromatic trend (or steeper-when-brighter trend) appears on intra-day and long timescales. The RWB trend is dominated by the radiation of accretion disk and jet, and resembles those in flat spectrum radio quasars. When PMN J0948+0022 is brighter than 17.m5 in the R band, there is no color change trend. By analyzing the spectral data of PMN J0948 +0022, we obtained the black hole mass of M = 1.61 × 107 $$M_{\odot}$$ and accretion rate of $$\dot{\mu} = 93$$, and confirmed that PMN J0948+0022 is a super-Eddington accreting NLS1. The redshifts of reverberation mapped super-Eddington accreting active galactic nuclei can be expanded by PMN J0948+0022 up to above 0.5. Super-Eddington accreting NLS1 galaxies were chosen as a new type of cosmological candle in the literature. PMN J0948+0022 may be used as a target for the next step of reverberation mapping monitoring project of super-Eddington accreting massive black holes.

Keywords

galaxies: jets – galaxies: photometry – galaxies: Seyfert – galaxies: active

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